Point-count bird censusing: long-term monitoring of bird abundance and diversity in central Arizona-Phoenix, ongoing since 2000

Bateman H., D. Childers, M. Katti, E. Shochat and P. Warren. 2017. Point-count bird censusing: long-term monitoring of bird abundance and diversity in central Arizona-Phoenix, ongoing since 2000. Environmental Data Initiative, http://dx.doi.org/10.6073/pasta/d6f29d5aba5b22c65b0656c86214958a.

Over the past half-century, the greater Phoenix metropolitan area (GPMA) has been one of the fastest growing regions in the US, experiencing rapid urban expansion in addition to urban intensification. This backdrop provides an ideal setting to monitor biodiversity changes in response to urbanization, and the CAP LTER has been using a standardized point-count  protocol to monitor the bird community in the GPMA and surrounding Sonoran desert region since 2000. The bird survey locations in this CAP LTER core monitoring program include six general site groupings including (1) bird survey locations from a subset of the CAP LTER’s Ecological Survey of Central Arizona long-term monitoring sites; (2) sites positioned in an area of intense study on the Arizona State University Polytechnic Campus (North Desert Village) in which the CAP LTER converted the landscaping of small neighborhoods to reflect the dominant landscaping preferences employed throughout the GPMA; sites (3) in riparian areas, (4) along the Salt River as it runs through the GPMA, (5) at desert parks that coincide with the CAP LTER Desert Fertilization (DesFert) experiment sites and (6) locations from what used to be a separate bird-monitoring effort (monitoring in Phoenix Area Social Survey neighborhoods).

Each bird survey location is visited independently by three birders who count all birds seen or heard within a 15-minute window. The frequency of surveys has varied through the life of the project. The first year of the project (2000) was generally a pilot year in which each site was visited approximately twice by a varying number of birders. The monitoring became more formalized beginning in 2001, and each site was visited in each of four seasons by three birders. The frequency of visits was reduced to three seasons in 2005, and to two season (spring, winter) beginning in 2006.

Most recent analysis paper derived from this dataset: Banville, M.J., Bateman, H.L., Earl, S.R. and P.S. Warren 2017: Decadal declines in bird abundance and diversity in urban riparian zones. Landscape and Urban Planning, 159, 48–61, https://doi.org/10.1016/j.landurbplan.2016.09.026.

In this study, Banville et al. examined long-term trends of bird assemblages specifically at the riparian sites within the greater Phoenix metropolitan area where the CAP LTER conducts bird censuses. Riparian habitat sites were classified as engineered or natural depending on the extent of human modification. The sites were further differentiated by the permanence of water as ephemeral versus perennial, with the latter having more vegetation and water. Engineered riparian habitats supported more urban-adapted species whereas natural riparian habitats supported more specialists. Overall, bird species richness, diversity, and abundance declined across all riparian types during the 12-year period of study even for common species. Results indicate that bird communities in natural settings have changed over the monitoring period more than communities at engineered sites, and that the riparian bird community is shifting toward more urban-dwelling species that are characteristic of riparian sites with less water and more impervious surface.

Successive ordinations of the riparian bird community in the greater Phoenix metropolitan area. Each ellipse reflects a 3-year moving average over a 12-year study period. Results indicate that the riparian bird community is shifting toward assemblages that are more reflective of those found at ephemeral-engineered (i.e., urbanized) riparian sites.


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